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Plane Geometry C1

Wirtz Plane Geometry Carnegie Chapter 1

Term

Definition

polygon

It is a two-dimensional figure that is formed by three or more segments called sides. Each side must intersect exactly two other sides, one at each endpoint. No two sides intersect each other more than once.

side (polygon)

In a polygon, it is one of any of the line segments that form the polygon.

triangle

It is a polygon with three sides.

quadrilateral

It is a polygon with four sides.

pentagon

It is a polygon with five sides.

octagon

It is a polygon with eight sides.

perimeter

It is the sum of all the side lengths.

area (polygon)

In a polygon, it is the number of square units needed to cover the figure.

rectangle

It is a parallelogram with four right angles.

length (quadrilateral)

In a quadrilateral, it is the top to bottom distance.

width (quadrilateral)

In a quadrilateral, it is the side to side distance.

base (rectangle)

In a rectangle, it is the side to side distance.

height (parallelogram)

In a parallelogram, it is the perpendicular distance between the two bases.

parallelogram

It is a quadrilateral in which both pairs of opposite sides are parallel.

vertex (polygon)

In a polygon, it is the point where two sides of the polygon intersect.

altitude

A perpendicular segment that indicates the height of a figure. It is drawn from a vertex to the opposite side or to the line that contains the opposite side.

base (triangle)

In a triangle, it is the side to which the altitude is drawn.

height (triangle)

In a triangle, it is the perpendicular distance from a vertex to the side opposite the vertex.

trapezoid

It is a quadrilateral with exactly one pair of parallel sides. The parallel sides are called bases and the nonparallel sides are called legs. The perpendicular distance between the bases is the height.

base (trapezoid)

In a trapezoid, it is the parallel sides.

height (trapezoid)

In a trapezoid, it is the perpendicular distance between the two bases.

regular polygon

It is a polygon whose sides all have the same length and whose angles all have the same measure.

apothem

It is the perpendicular distance from the center of a regular polygon to a side.

diameter

It is the distance across the circle through the center. It is equal to twice the radius of the circle.

circumference

It is the distance around a circle (like the perimeter of a polygon) and equal to pi multiplied by the diameter, d, or pi multiplied by twice the radius, r.

radius

It is the distance from the center of a circle to a point on the circle.

irrational number

It is a number that cannot be written as a/b, where a and b are integers.

area (circle)

In a circle, it is the number of square units needed to cover the figure.

composite figures

It is formed by two or more figures.

base of a geometric figure

In a geometric figure, it is the side or face to which an altitude is drawn, or is considered to be drawn.